Various technologies to measure the surface shape of an object, such as industrial products, have been proposed, and an optical three-dimensional shape measuring device is one of these. There are various types and configurations of optical three-dimensional shape measuring devices, and one of these implements that projecting a predetermined projection pattern (e.g. slit light, stripes) onto a test object, taking an image of the test object, and measuring the height of a reference plane of each image position (each pixel) based on the captured image, for measuring the three-dimensional surface shape of the test object (see Patent Document 1).
Such a device is constructed such that a slit projection pattern formed of one slit light is projected onto the surface of the test object, and an image of the slit projection pattern projected onto the test object from an angle different from the projection direction is picked up every time the slit projection pattern is scanned on the entire surface area of the test object, the height of the surface of the test object from a reference plane is calculated using such a principle as trigonometric measurement for each pixel in a longitudinal direction of the slit projection pattern based on the picked up image of the surface of the test object, and the three-dimensional shape of the surface of the test object is determined.
FIG. 9 shows a configuration example thereof, where the slit light 52 is projected from the slit pattern projection unit 51 and a slit projection pattern is projected onto the surface of a test object 53 placed on a supporting stand 56. The slit projection pattern projected onto the surface of the test object 53 is transformed according to the three-dimensional shape on the surface of the test object 53, and every time the slit projection pattern is scanned onto the entire surface of the test object 53 by moving the supporting stand 56 in a direction different from the longitudinal direction of the slit projection pattern (e.g. arrow direction in FIG. 9) by a supporting stand moving device (not illustrated), the transformed slit projection pattern of the surface of the test object 53 is picked up by the imaging device 55 (e.g. CCD sensor) via an imaging lens 54 in an angle different from the projection direction, and is sent to a processing unit 57 where the captured image data is computed. In the processing unit 57, the height of the surface of the test object from the reference plane is calculated for each pixel of the slit projection pattern in the longitudinal direction using the principle of trigonometric measurement based on the captured image data on the surface of the test object picked up in this way, thereby determining a three-dimensional shape of the test object surface.    Patent Document 1: Japanese Patent Application Laid-Open No. 2000-9444